Field of the Invention
The present invention relates, in general, to rotary cutting tools or bits and, specifically, to combined drill/reamer bits.
In machining operations for forming bores in metallic workpieces, rotary cutting tools, such as drills bits, are commonly employed. Such drill bits are mounted in a spindle which rotates the bit at high speed and advances the bit at a predetermined feed rate into the workpiece.
Depending upon the material of the workpiece, the feed rate of the drill bit which comprises its rate of advance into the workpiece and its speed of rotation are selected to provide a finished bore having required tolerances in location, diameter, concentricity and surface finish. However, in certain instances, bore diameter tolerances cannot be held unless several passes are made with the drill or a ream finish operation is employed. Such steps add to manufacturing costs due to the increased time required to manufacture a workpiece and the added cost of additional bits and spindles for successive drilling and reaming operations on a single workpiece.
Attempts have been made to address these problems by devising combined drill/reamer bits which perform both drilling and reaming operations in a single pass.
Although such previous drill/reamer bits solve or minimize many of the problems noted above, it would still be desirable to provide a combined drill/reamer bit which performs a machining operation in a single pass with a high degree of tolerance. It would also be desirable to provide drill/reamer bit which can be easily modified for different applications.